1. Field of the Invention
The present invention relates to an image capturing device, and in particular, to an image capturing device that captures an image by using a CCD that is enclosed in a chamber.
2. Related Art
Devices such as lumino image analyzers for detecting and analyzing chemiluminescence and bioluminescence, cameras for astronomical observation, and the like must capture weak light, and therefore, an ultra-high sensitivity cooling CCD camera is used in these devices.
In an ultra-high sensitivity cooling camera, in order to capture weak light, the CCD is cooled to −20° C. to −30° C. so as to suppress dark noise, and further, the chamber that accommodates the CCD is shielded from light such that light, other than the light for which capture is intended, does not enter the CCD.
As such a chamber, there is a sealed container for CCD cooling having: an FPC substrate on which a CCD is placed, and that supplies electric power for cooling to a CCD sealed container, and is for outputting image signals obtained by the CCD; a first cover that seals a first surface of the FPC substrate; a first seal member that is provided at the contacting portion of the FPC substrate and the first cover; a second cover that seals a second surface of the FPC substrate; and a second seal member that is provided at the contacting portion of the FPC substrate and the second cover. (Refer to Japanese Patent No. 3309429.)
However, when cooling the CCD that is accommodated in the chamber, the humidity within the chamber greatly decreases, and therefore, moisture at the exterior of the chamber is drawn into the interior of the chamber.
Further, if moisture penetrates into the chamber, there may be a case in which water stays between the electrodes of the Peltier element that is provided in the chamber in order to cool the CCD, and the electrodes short-circuit so poor cooling occurs. Further, if moisture adheres to the wiring within the chamber, such as the terminal portions of the CCD, and the electrode portions of the CCD substrate and the flexible substrate, and the like, these terminals may corrode or electricity may be conducted between these terminals, so there is the possibility that noise will increase.
Thus, an attempt has been made to prevent moisture from penetrating into the chamber by changing the seal, that is between the chamber and the flexible substrate that connects the CCD to an external electronic circuit, to an O-ring that is made of a fluorine rubber and has low moisture absorption, or by changing the material of the flexible substrate to a polyimide resin that has low moisture absorption.
Effects of a certain extent can be seen owing to these measures, but the preventing of penetration of moisture into the chamber interior is incomplete.